Friday, December 29, 2006

The Inner Sleep Clock

The Underlying System that Governs Our Sleep and EnergyHave you ever wondered? How some people can wake up at precisely the sametime every morning without an alarm clock? Perhaps you've had this happen toyourself a number of times, or maybe it happens already.Also, why is it that we have alarm clocks to tell us when to wake up, but very fewpeople have alarm clocks to tell them when to go to sleep? I know, it's kind of astupid question, but there's actually a reason behind it, and you're about to find outwhy.There is an underlying mechanism, called the sleep clock, which consists of anumber of variables in your body that tell it when to feel tired, and when to feelawake. It also controls how deep you sleep, and how long you sleep.Refer to the chart below:Neat eh? But what does it mean? Ha...Circadian rhythmThe first, and most important part of your sleep clock is your body temperaturerhythm. It’s also known as a circadian rhythm.Contrary to what most of us are taught in grade 5 science class, our bodytemperature doesn't stay at a constant 98.6º Fahrenheit (37º Celsius). Our bodytemperature actually has a specific rhythm to it. It rises and drops as the hours of theday progress. The difference in body temperature is about 3º Fahrenheit (2º Celsius)This periodic rise and drop in body temperature tells our mind when to feel tired andwhen to feel more awake. As body temperature rises, we tend to feel more awakeand our brain waves are usually higher. As body temperature drops, we tend to feelmore lethargic, tired, and lazy - this is a big cue for our minds to lower brain wavesand enter Stage 1 sleep.As you look at the graph again, you might notice that there is a slight “drop” of bodytemperature during the mid afternoon. This is a usual mid-afternoon bodytemperature slump. You may have noticed, at some point in your life, that youusually feel an urge to sleep or take a nap during the afternoon. This is completelynatural, and sometimes the pressure to sleep during the afternoon is as strong asthe pressure at night! (Although most of us chose a drug of choice, such as caffeine,to combat this body slump).Because of the demands our society puts on us, such as work, children, and sociallife, most of us can't sleep at this time. As we'll explore later on, nature actuallyintended for us to have a nap at this time - we'll talk about the science of naps indetail.Generally, body temperature begins to rise in the early morning hours, dropssometime during the afternoon, then begins to rise until the early hours of theevening. It's at this time that we have “peak performance” body temperature, mostpeople are most active during the early evening hours, this is where bodytemperature is the highest. Afterwards, body temperature drops and reaches itslowest point at around 4 am.If your body temperature rhythm is too flat (doesn't rise or drop low enough), or if it'smessed up in any other way, chances are you will experience sleep difficulties. It willbe difficult for you to sleep deeply. We'll explore all the causes of that later on in thise-book.It's because of the body temperature rhythm that most of us feel sleepy, at preciselythe same time every night. It's also why some people can wake up without an alarmclock at precisely the same time every morning.Usually, your body temperature rhythm will follow the same pattern regardless ofwhen you fall asleep. For instance if you've been waking up at 7 AM all your life, thismeans your body temperature begins to rise at this time. It won't matter if you fallasleep at 11 PM, 12 AM, or 1 AM, your body temperature will rise at 7 AM, and youwill feel sleepy at the same time you always did the next day. Unless you take theproper actions to optimize your body temperature, it will usually return to the samepattern. This is the main focus of this book.This is the primary reason why jet lag happens. When you travel really quicklyacross several time zones, your body may be in a different time zone, but yourtemperature rhythm is still following the pattern it did before!So if you normally live in Florida, and you take a flight to California; if it's 8 PM inCalifornia, your body will still think it's 11 PM, based on your temperature rhythm. Asyou see, your temperature rhythm really acts as an internal “clock”.Your body temperature rhythm can adjust to a new time zone, or a new sleepingpattern, and this may take from a few days to up to several weeks! This is whytrans-continental jet lag is so severe for some people.Your body temperature rhythm is perhaps the most important concept to grasp aboutyour inner sleep clock. It has a huge impact on how you sleep, and how you functionduring the day.So what affects your body temperature rhythm? And how could someone possibly“damage” their body temperature rhythm?The second important element of your sleep clock is your melatonin hormone level,and your exposure to natural sunlight.Melatonin and SunlightHave you ever wondered why human beings sleep at night? Did someone just makethe decision one day: “Okay Guys! From now on we're all going to go to sleep whenthe big light in the sky turns off!”That could possibly be it! But there's actually a system inside of us that uses lightand darkness to control certain sleep hormone levels.Melatonin is a hormone synthesized in the pineal gland and, to a lesser extent, inthe retina. Melatonin is responsible for putting you to sleep and restoring physicalenergy while we sleep. If your melatonin levels are high, you will experience feelingsof drowsiness, loss of energy, etc.Melatonin is released when we're exposed to darkness. The instant sunlight stopsentering our eyes, our melatonin hormone level begins to rise. Your melatonin levelsare EXTREMELY dependant on the amount of natural sunlight that enters your eyesduring the day!Higher exposure to sunlight delays the body temperature drop, and lets you stayawake and alert longer. Poor exposure to sunlight will promote a quick temperaturedrop and make you feel sleepy, tired, and out of balance. You will most likelyexperience the pressure to sleep very early in the day, or the pressure to sleep willbe very minimal which might cause insomnia and poor quality sleep.Because melatonin is released when we're exposed to darkness, it is alsosometimes called the vampire hormone.We'll explore exactly how important sunlight is in a later part of this book. Howeverit's important to understand that getting proper sunlight isn't an “optional” part of thisprogram, it's a MUST, as it is the main way our body adjusts our body temperaturerhythm.Activity LevelThe amount of movement and cardiovascular exercise you get during the night has ahuge impact on your body temperature rhythm. Any movement or exercise promotesa quick rise in temperature which can be very beneficial to the sleep system.Exercise creates a higher “peak” point of body temperature during the day, which willincrease your energy levels far beyond anything else. Exercise delays the bodytemperature drop at the end of the day, allowing you to stay awake and alert longer.Finally, exercise will make the drop of body temperature at the end of the day moredrastic and allow your body temperature to stay lower for a longer amount of time;this will promote much deeper sleep.Prior WakefulnessObviously the amount of time you're awake has a direct effect on all three factorsabove. Your activity levels contribute a lot to your temperature variations. Also, thelonger you're awake obviously means you get more potential for sunlight entry intoyour eyes, which has a direct effect on your melatonin level.If you're currently sleeping 8 or 9 hours and you feel tired during the day this couldactually be a sign that you need LESS sleep. You're sleeping too much and youneed to increase your prior wakefulness to create deeper sleep and a more balancedbody temperature rhythm.The four factors up above control how long you sleep, and how deep yoursleep is. To summarize, the factors that affect your sleep the most.1) The body temperature rhythm.2) Natural sunlight entering your eyes, as it has a direct effect on your melatoninlevels.Understanding how the body temperature rhythm affects your sleep is the key tooptimizing your sleep. The body temperature rhythm is really what makes the sleepclock a... “Clock”.Usually, your body temperature follows the same pattern regardless of when you goto sleep. For instance, if you routinely get up at 8 am every day, this means yourbody temperature begins to rise at 8 am. If you feel drowsy for the next 3 hours, thismeans your body temperature is slowly rising during this time, and hasn't reached it'speak point. For most people the optimum peak point of body temperature is ataround 6 PM to 7 PM, this is when we are naturally most active and have the mostenergy. Study the previous graph if you still aren't clear about how the bodytemperature rhythm flows.If all of a sudden you revert to waking up at 6 AM instead of 8 AM, this doesn't meanthat your body temperature will begin to rise at 6 AM, it will remain low and begin torise at 8 AM like it usually did, and possibly making you feel drowsy for 5 hoursinstead of 3. Unless you expose yourself to high-intensity light, as we'll explore soon.This is why it is so hard to force yourself to wake up early, and why the popular beliefpersists that waking up earlier than usual is painful!This natural “clock” is also why some people do not need an alarm clock to wake upat PRECISELY the same time every day. This isn't a mysterious psychic force theyhave; their body temperature simply rises at precisely the same time everyday.In the next section we'll examine all the details of optimizing your sleep clock.Section SummaryTake this short quiz to better learn and remember what you've just read.1. What best describes deep sleep?a. Super high brain waves, twitching muscles and rapid eye movement.b. A type of human hibernation, we can use deep sleep to sleep past really coldtimes.c. Low brain waves, respiration, heart rate, and blood pressure. Dilated bloodvessels to allow blood to the muscles.2. What is the sleep clock?a. A system inside your body that counts the time until your inevitable death.b. A system that measures blood pressure to determine when it's time to sleep andwhen it's time to be awake and alert.c. A system that measures light intensity and body temperature to determine when tosleep, and how physically recharging your sleep is.3. We sleep during the night because...a. We're all vampires except we're not aware of it because we enter a different stateof consciousness while we're out partying with Dracula.b. It just seems like a good idea to sleep at night so we all do it.c. Melatonin is produced during the day which prevents us from sleeping.d. Melatonin is produced when we're exposed to darkness, which causes us to feelsleepy and our brain waves to lower.4. Our immune system turns on to fight diseases in what sleep stage?a. Stage 1b. Deep Sleep (stage 3 & 4)c. REM sleepd. When we're sleep walking or snoring.